1 error[E0658]: parenthetical notation is only stable when used with `Fn`-family traits
2 --> $DIR/unboxed-closure-feature-gate.rs:13:20
4 LL | let x: Box<dyn Foo(isize)>;
7 = note: see issue #29625 <https://github.com/rust-lang/rust/issues/29625> for more information
8 = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
10 error: aborting due to previous error
12 For more information about this error, try `rustc --explain E0658`.